ok if u take length to be x and width to be w
length=x
width=w
width is 6ft less than length so:
w=x-6
the equation for area:
area=length.width
area=x.w
area=x.(x-6)
area is 75ft
so
75 = x(x-6)
75=x^2-6x
as a quadratic
x^2-6x-75=0
after this use the quadtractif formula to find x which is length
then subsitute it into
75=x.w
to find width
+4 
+6 
